The invention relates to a method and apparatus for a service-interval display for engines, motor vehicles and the like, which generates a signal when a limiting parameter value is reached.
In known displays of this type, the distance travelled serves as the parameter. Consequently, the actual load on the engine, on which a majority of the servicing is performed, is insufficiently monitored. Hence, servicing is usually performed much earlier than engine load or wear require. The limiting value for the distance travelled must be set so that servicing is performed at the correct time even under extreme conditions, as for example in cold starting followed by hard acceleration. Furthermore, the criterion of the distance travelled either completely or insufficiently monitors several especially wear-intensive operating conditions, for example, warming up the vehicle at rest or accelerating hard with the engine cold.
The goal of the invention is to provide a display of the type recited hereinabove, which indicates that servicing is necessary precisely when it is in fact required.
The solution to this problem consists of using the total fuel consumption as a parameter.
It will be understood that at least one way of measuring total consumption is to determine the fuel consumed from some arbitrary point in time. Such a point in time will, of course, be different for different engines and for different operating circumstances. Thus, for a new engine, the starting point for measuring may be the instant of initial operation.
For other engines the starting point may immediately follow the carrying out of a particular maintenance operation.
This criterion permits monitoring both the above-mentioned extreme operating states and normal driving conditions, in a surprisingly simple manner, completely and with precise relationship to the actual engine wear. For example, if a given speed is assumed, fuel consumption decreases when the engine is operated more gently and increases directly with the load imposed on the engine. Hence, the load on the engine at a given moment has a direct correlation to the fuel consumption at the same instance. Consequently, total fuel consumption is a good measure of total engine wear.
It has been found that total fuel consumption can be the only parameter monitored for determining the need for servicing to compensate for engine wear. Since instantaneous fuel consumption displays are already often found in motor vehicles nowadays, total consumption can be determined simply by adding the instantaneous consumption values. Thus, it is only necessary merely to add a memory to create a circuit for the display according to the invention.
However, in order for the display function to conform to existing regulations, another parameter, for example the total distance travelled, must also be monitored. In some countries, a signal to indicate the need for servicing must be displayed after a predetermined distance has been travelled. Moreover, the additional parameter may improve the above arrangement. The instantaneous fuel consumption can be estimated when the additional parameter reaches an extreme value. Such parameters include, for example, engine oil and coolant temperature or engine rpm.
Within the scope of the invention, an additional advantageous measure can consist of dividing a predetermined maximum total fuel consumption into equal intervals, and assigning a pilot light to each of these intervals, said lights being extinguished at the end of the corresponding interval. By dividing into intervals in this fashion, an especially stressful driving style can be identified even before the maximum total consumption value is reached, since the pilot lights for the corresponding intervals will be extinguished more notably.
Often, it will suffice merely to turn on the pilot lights before starting the engine and turn them off when the engine starts, or afterward. Thus, each time he starts the vehicle, the driver is provided with information on approximately how long it will be until servicing is required. He can adjust his driving style to postpone this time as long as possible. In addition, he is not disturbed by the pilot lights as he drives.
In addition to the pilot lights, warning lights for the same total consumption intervals can be switched on continuously when the maximum total fuel consumption value is exceeded. The driver then receives information regarding the necessity of maintenance with increasing urgency.
This urgency can be intensified by making each of the consumption intervals employed after exceeding the maximum total fuel consumption smaller than the intervals comprising the maximum total level consumption. In this case more warning lights appear at shorter intervals, and stay on to provide a constant reminder to service the vehicle. For example, the intervals employed after maximum total fuel consumption have been reached may be one-half the size of the intervals used before maximum total fuel consumption is reached.
In order to ensure that vehicles which are not driven often will also have their service intervals indicated, a fixed time can also be combined with the maximum total fuel consumption, after which time a signal will likewise appear. In these cases, service becomes necessary as a result of aging phenomena, affecting, for example, the operating fluids used; these are phenomena which are not taken into account in vehicles which undergo average service.
Alternatively, a warning signal can appear independently of the total fuel consumption signal when the fixed time has elapsed. This signal can be used, for example, to indicate that additional maintenance is required such as touching up the undercoating.